Antioxidants for mineral oil lubricants and compositions containing the same



Patented June 27, 1950 ANTIOXIDANTS FOR MINERAL OIL LUBRI- CANTS ANDCOMPOSITIONS CONTAINING THE SAME sylvania No Drawing. ApplicationNovember 19, 1948, Serial No. 61,114

16 Claims. (cl. 252-515) This invention relates to antioxidants formineral oil lubricants and compositions containing the same, and moreparticularly, it relates to addition agents for mineral oil lubricantswhich inhibit the oxidative deterioration of said lubricants.

In the lubrication of internal combustion engines of all types,particularly when severe operating conditions are encountered, plainmineral lubricating oils often prove unsatisfactory in service becauseof the oxidative deterioration of the oil, with the attendant depositionon the engine surfaces of varnish, gum or sludge. Furthermore, manylubricating oil compositions which may be highly satisfactory for thelubrication of other mechanisms have been found wholly unsuitable foruse as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is dueat least in part to oxidation efiects on mineral lubricating oils. Inturbine oils the problem of oxidation is further aggravated, because innormal use turbine oils rapidly become contaminated with water.

It is an object of this invention, therefore, to

provide an addition agent for mineral oil lubricants which will inhibitthe oxidative deterioration of such lubricants.

. It is a further object of this invention to pro-- vide improvedmineral oil lubricant compositions which are remarkably stable againstoxidation under service conditions.

These and other objects are accomplished by the present inventionwherein an addition agent for mineral oil lubricants is prepared bycondensing diethylaminobenzaldehyde, N-dimethylaniline and formaldehydein the presence of an activated clay catalyst, and recovering thecondensation product. The condensation product so obtained is alight-colored product which, when added to mineral oil lubricants,confers a remarkable stability against deterioration by oxidation. Suchcondensation products and the mineral oil lubricant compositionscontaining them are believed to be novel and are considered parts of ourinvention. Contrary to what may be expected from the nature of thereactants, we do not obtain highly-condensed, insoluble resinousproducts. On the contrary, when the above reactants are condensed inaccordance with Our invention, there are obtained light-coloredcondensation products which are non-resinous and which are readilysoluble in mineral oils.

In performing the condensation, the reactants are mixed and heated to amaximum temperature of 350 F. We have found that if the temperature of350 F. is exceeded to any substantial extent, the condensation productformed tends to be resinous and insoluble. In general, the preferredline solids.

temperature for the condensation ranges from to 280 F. The proportionsof the reactants may vary over a fairly wide range. For each mol ofdiethylaminobenzaldehyde, there is employed 1 to 4 mols ofN-dimethylaniline and 1 to 4 mols of formaldehyde. Ordinarily, it ispreferred to use from 5 to 10 per cent by weight of the activated claycatalyst, based on the total weight of the reactants. However, smalleramounts, as low as 1 per cent by weight, and larger amounts, as high as20 per cent by weight, may also be employed; but larger amounts thanabout 10 per cent by weight are ordinarily not necessary. In lieu offormaldehyde, any formaldehyde yielding compound, such asparaformaldehyde, dioxymethylene and trioxymethylene may be employed. Insuch case, the amount of formaldehyde-yielding compound used is based onthe equivalent number of mols of formaldehyde yielded within the rangeof proportions of formaldehyde set forth hereinabove. Accordingly, asused in the appended claims, the term formaldehyde is intended toinclude formaldehyde-yielding compounds as well as formaldehyde itself.

Various activated clay catalysts may be employed in accordance with ourinvention. Such materials are well known in the art and comprise anatural clay, such as bentonite, fullers earth,

floridin and smectite, which has been acid treated in order to activatethe clay. These materials are described in U. S. Patent 1,898,165, forexample.

In preparing our new addition agents, the reactants and catalyst areplaced into a reaction vessel which is then closed and the mixtureheated with agitation under reflux until all of the formaldehyde orformaldehyde-yielding compound has been consumed. At this time, thewater which is formed as a result of the condensation is removed.preferably under vacuum, and the dehydrated condensation product is thenfiltered to remove the activated cla catalyst. In some instances, it isdesirable to prepare our new addition agent in a concentrate in amineral lubricating oil which may then be diluted down with additionaloil to the concentration desired in the final lubrieating composition.In such instances, the mineral lubricating oil may be added in asuitable.

amount, say in a weight equal to the weight of reactants, to thereaction mixture in the reaction vessel, and the condensation productobtained will then be a concentrated solution of the addition agent inthe mineral lubricating oil.

The condensation products obtained in accordance with our invention areliquids or crystal- While the exact nature of the chemical compositionof the condensation products is unknown all of the three reactants enterinto a final unitary product. The exact manner in which the catalystinfluences the. reaction is unknown. However. regardless of any theoryinvolved, the use of an activated clay catalyst is an essential featureof our invention, since if the catalyst is omitted, black, insoluble,resinous condensation products are obtained.

The following examples illustrate the preparation of our new additionagent.

Example I.Into an enamel-lined reaction vessel, equipped with means foragitation and a reflux condenser, there were placed 1'77 pounds (1 poundmol) of p-diethylaminobenzaldehyde, 242 pounds (2 pound mols) ofN-dimethylaniline, 162 pounds (2 pound mols of anhydrous formaldehyde)of a 37 per cent by weight aqueous solution of formaldehyde, and 40pounds (about 6.5 per cent by weight of the reactants) of Filtrol (anactivated montmorillonite) as a catalyst. The mixture was agitated andrefluxed at 280 F. for 5 hours, and then all water, both that added withthe formaldehyde and formed in the reaction, was distilled off byfurther heating at 280 F. and the product dried. The product was thenfiltered through Celite, a diatomaceous earth filter aid. The producthad the following properties:

Specific gravity 60/60 F 1.0374 Color, NPA 3.5 dil. Neutralization No..422

Example II.-An addition agent was prepared by reacting 1 mol ofp-diethylaminobenzaldehyde, 4 mols of formaldehyde and 4 mols ofN-dimethylaniline in the presence of per cent by weight of the totalreactants of an activated montmorillonite catalyst (Filtrol) under theconditions set form in Example I. The product had the followingproperties:

' Specific gravity, 60/60 F. 1.0246

Color, NPA 3.5 Neutralization No. 2.7

Specific gravity, 60/60 F. 1.071 Color, NPA 3.5 Neutralization No. 4.1

The-condensation products obtained in accordance with the abovedisclosure from diethylaminobenzaldehyde, N-dimethylaniline andformaldehyde in the presence of an activated clay catalyst are excellentaddition agents "for mineral oil lubricants. They are readily soluble inall types of mineral oils, that is, parafflnic, naphthenic or mixed basemineral oils and can be blended with mineral oils in high proportions toform concentrated solutions thereof, which may then be diluted down tothe proportions desired in the final mineral oil lubricant composition.As stated, our new addition agents are remarkably effective ininhibiting the oxidative deterioration of mineral oil lubricantcompositions. For this purpose small amounts of our new addition agentsare generally sumcient. For

example, our addition agents may be added to mineral lubricating oils inminor amounts, say from 0.001 to 1 per cent by weight on the mineraloil, sufficient to inhibit the oxidative deterioration ble antioxidanteffects of our new addition agents.

In the following examples, the base oil and the same oil blended withour new addition agents are subjected to a standard oxidation test whichmeasures the stability of the oils to oxidation. The oxidation testreferred to is a standard test designated ASTM D943-47T. Briefly, thetest comprises subjecting the oil sample to oxygen at a temperature ofC. (203 F.) in the presence of water and an iron-copper catalyst, anddetermining the time required to build up a neutralization number of 2.The flow of oxygen is maintained at 3 liters per hour. The remarkablyeffective stability to oxidation of mineral oil lubricant compositionscontaining our new addition agents is illustrated by the results shownin the following examples.

Example IV.To a refined turbine oil base, there was added 0.5 per centby weight of the addition agent prepared in accordance with Example I. Acomparison of the base oil and improved oil follows:

Base Oil Improved Oil Gravity, API 29.4 29.4 Viscosity, SUV: 210 F 53.052. 9 Color, NPA 2.0 2.0 Neutralization No 0. 01 0.02 Oxidation 'Icst,ASTM D043-47'I 203 F., 3 L. Oxygen per Hr.:

Time Oxidized, Hrs 180 3395 Neutralization No 2. 0 2.0

Example V.-An improved motor oil was prepared by adding 0.5 per cent byweight of the addition agent prepared in accordance with Example II to amotor oil base. A comparison of the base oil and the base oil blendedwith the antioxidant showed the following results:

Base Oil Improved Oil Gravity, API 32. 5- 32. 5 Oxidation Test ASIMD943-47I 203 F., 3 L. Oxygen per Hn:

Time Oxidized, Hrs 210 3, 500 Neutralization No 2.0 2.0

to be either prooxidant or to show no antioxi-' dant effects whatsoever.For example, we have prepared a condensation product similar to our newaddition agents by substituting xylidine for N-dimethylaniline. Theresulting condensation product was found to be entirely unsuitable forinhibiting the oxidative deterioration of mineral oil lubricantcompositions.

While we have shown in the examples the preparation of compoundedlubricating oils, our invention is not limited thereto but comprises allmineral oil lubricant compositions containing our new addition agents,such as greases and the like. If desired, other known addition agentsmay be incorporated into the lubricant compositions prepared inaccordance with our invention. For example, pour point depressants,extreme-pressure agents, viscosity index improvers and the like may beadded.

Resort may be had to such modifications and variations as fall withinthe spirit of the invention and the scope of the appended claims.

We claim:

1. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating diethylaminobenzaldehyde with from 1 to 4 molsof N-dimethylaniline and 1 to 4 mols of formaldehyde per mol ofdiethylaminobenzaldehyde in the presence of an activated clay catalystat a temperature not in excess of 350 F. to condense together the threereactants, and recovering the condensation product.

2. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating diethylaminobenzaldehyde with from 1 to 4 molsof N-dimethylaniline and 1 to 4 mols of formaldehyde per mol ofdiethylaminobenzalde- 'hyde in the presence of 5 to 10 per cent byweight on the total reactants of an activated clay catalyst at atemperature of from 160 to 280 F. to condense together the threereactants, and recovering the condensation product.

3. The process of preparing. an addition agent for mineral oillubricants which comprises adding an activated clay catalyst,diethylaminobenzaldehyde with from 1 to 4 mols of N-dimethylaniline and1 to 4 mols of formaldehyde per mol of diethylaminobenzaldehyde to amineral lubricating oil, heating the mixture to a temperature not inexcess of 350 F. to form a condensation product of the three reactants,and recovering a solution of the condensation product in the minerallubricating oil.

4. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating 1 mol of diethylaminobenzaldehyde, 2 mols ofN-dimethylaniline, and 2 mols of formaldehyde in the presence of about 6per cent by weight on the total reactants of an activated clay catalystat a temperaature of from 160 to 280 F. to condense together the threereactants, and recovering the condensation product.

5. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating 1 mol of diethylaminobenzaldehyde, 4 mols ofN-dimethylaniline and 4 mols of formaldehyde in the presence of about 10per cent by weight on the total reactants of an activated clay catalystat a temperature of from 160 to 280 F. to condense together the threereactants, and recovering the condensation product.

6. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating 1 mol of diethylaminobenzaldehyde, 1 mol of-dimethylaniline and 1 mol of formaldehyde in the presence of about 1the total reactants of an at a temperature of from 160 to 280 F. tocondense together the three reactants, and recovering the condensationproduct.

7. A non-resinous condensation product of diethylaminobenzaldehyde withfrom 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehydeper mol of di'ethylaminobenzaldehyde', said per cent by weight onproduct being obtainable by the process of claiml.

activated clay catalyst 11. A lubricant composition comprising a majoramount of a mineral lubricating oil, and a minor amount, sumcient toinhibit the oxidative deterioration of said oil of a non-resinouscondensation product of diethylaminobenzaldehyde with from 1 to 4 molsof N-dimethylaniline and 1 to 4 mols .of formaldehyde per mol ofdiethylaminobenzaldehyde, said product being obtainable by the processof claim 1.

12. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, from 0.001 to 1.0 per cent byweight of said oil, of a non-resinous condensation product ofdiethylaminobenzaldehyde with from 1 to 4 mols of N-dimethylaniline and1 to 4 mols of formaldehyde per mol of diethylaminobenzaldehyde, saidproduct being obtainable by the procnet is 0.5 per cent by weight ofsaid oil.

15. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, sufiicient to inhibit the oxidativedeterioration of said oil of a non-resinous condensation product of 1moi of diethylaminobenzaldehyde, 4 mols of N-dimethylaniline and 4 molsof formaldehyde, said product being obtainable by the process of claim5.

16. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, sumcient to inhibit the oxidativedeterioration of said oil, of a non-resinous con-' densation product of1 mol of diethylaminobenzaldehyde, 1 mol of N-dimethylaniline and 1 molof formaldehyde, said product being obtainable by the process of claim6.

- HERSCHEL G. SMITH.

TROY L. CAN'IRELL. 00 G. PETERS.

ERENQ H The following references are of record in the file of thispatent:

Number Name A Date 1,584,473 Regal May 11. 1926 1,873,799 Vacher Aug.23, 1932 1,954,484 Mattison Apr. 10, 1934 2,113,599 Musselman Apr. 12,1988 2,294,726 Dreshneld Sept. 1, 1942 2,336,006 Fuller Dec. 7, 19432,375,168 'Hardman May 1, 1945 2,453,850 Mikeska Nov. 16, 1948 2,454,890Smith et a1. Nov. 30, 1948

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTSWHICH COMPRISES HEATINT DIETHYLAMINOBENZALDEHYDE WITH FROM 1 TO 4 MOLSOF N-DIMETHYLANILINE AND 1 TO 4 MOLS OF FORMALDEHYDE PER MOL OFDIETHYLAMINOBENZAIDEHYDE IN THE PRESENCE OF AN ACTIVATED CLAY CATALYSTAT A TEMPERATURE NOT IN EXCESS OF 350*F. TO CONDENSE TOGETHER THE THREEREACTANTS, AND RECOVERING THE CONDENSATION PRODUCT.